Upstroke -cushioning expansible strut

ABSTRACT

This upstroke-cushioning expansible strut consists of a springpressed hollow upper inner arm having on its lower end a piston head reciprocable within a roughly cylindrical hollow lower outer arm, the formed being pivoted to an automobile rear hatch while the latter is pivoted to the lower part of the automobile body. Mounted between the lower arm and the upper arm is an elongated hollow spool-shaped internal seal which also guides the upper arm as it is propelled upward by the lifting force applied by the operator, assisted by internal springs. The air is allowed to escape gradually through bleed orifices until the upper arm nears its fully extended position, whereupon the release of the air is halted by the covering up of the orifices by the internal seal when said orifices reach said seal, thereby cushioning the impact which would otherwise occur between the piston head on the lower end of the upper inner arm and the upper end of the lower outer arm. The internal seal also acts as a resilient stop.

[ Nov. 4, 1975 UPSTROKE-CUSHIONING EXPANSIBLE Primary Examiner-James B.Marbert Attorney, Agent, or Firm-Willis Bugbee STRUT [76] Inventors:Werner H. Fengler; Richard R.

[ ABSTRACT This upstroke-cushioning expansible strut consists of aFengler, both of 23651 Fordson Drive, Dearbom, Mich. 48124 June 3, 1974spring-pressed hollow upper inner arm having on its [22] Filed.

lower end a piston head reclprocable within a roughly cylindrical hollowlower outer arm, the former being Appl. No.: 475,505

I pivoted to an automobile rear hatch while the latter is Re ated UsApphcatlon Data pivoted to the lower part of the automobile body.

Mounted between the lower arm and the upper arm is an elongated hollowspool-shaped internal seal which also guides the upper arm as it ispropelled upward by the lifting force applied by the operator, assistedby internal springs. The air is allowed to escape gradually throughbleed orifices until the upper arm nears its fully extended position,whereupon the release of the 2, $5.4, 7 ll w H5 3 7 8 161 0 2 m 6 N 5 M8 m 3 7 w 6 9 w o 4 n on w 0 "/00 2 700 o M 3& N 7 u .4 6 m "3 a 2 W N SMW Z ml 0 mmc m m .l m 1 mm L2?! 0 I06 FWC-GZ mv m Ca U.mF l 1]] 3 2 8 6555 l [.ll.

188/322; 277/212 207; 16/66 air is halted by the covering up of theorifices by the 56] References Cited internal seal when saicl'orificesreach said seal, thereby UNITED STATES PATENTS cushioning the impactwhich would otherwise occur between the piston head on the lower end ofthe upper 267/65 R inner arm and the upper end of the lower outer arm.

8 The internal seal also acts as a resilient stop.Doetsch................................ 267/34 9/1920 DunnWyeth................

21 9 Claims, 5 Drawing Figures II'I'IIIIIII'IIII B Ill In l'llllilvlrllll US. Patent N0v.4,1975 3,917,245

UPSTROKE -CUSHIONING EXPANSIBLE STRUT This application is a continuationof our prior copending application Ser. No. 304,853, filed Nov. 8, 1972,now abandoned.

BACKGROUND OF THE INVENTION Certain recent models of automobile bodiesat their rearward ends have been equipped with hatches pivoted at theirupper ends to the roofs of the bodies and provided on their oppositesides with spring-pressed expansible struts for holding the hatch openwhile its raised position during loading or unloading of the automobilebody. With small automobile bodies having light-weight hatches, thisconstruction was successful, but when it was applied to largerautomobile bodies with correspondingly heavier hatches, the heaviersprings required to counterbalance the heavier weights caused a violentshock by the inpact of the lower end of the upper strut arm at the endof its stroke against the upper end of the lower strut arm. This in turncaused damage to the car body and breakage of the strut.

SUMMARY OF THE INVENTION The present expansible strut prevents thismetal-tometal clashing of the upper and lower strut arms, as the upperarm nears the end of its upward stroke, by providing cushioning meansfor the final part of the stroke of the upper strut as its lower endnears its engagement with the upper end of the lower strut. Thisprevents the hatch hinge breakage which previously has frequentlyoccurred in prior hatch constructions when the hatch is thrown upwardand halts abruptly under the excessive force of the powerfulcounterbalancing springs, es pecially in large heavy hatches forcorrespondingly large vehicles. The spool-shaped internal seal betweenthe outer and inner arms also serves as a resilient stop and likewiseprovides additional guidance for the greatly elongated telescoping armsat locations intermediate their opposite ends. In the drawings,

FIG. 1 is a central vertical longitudinal section through anupstroke-cushioning expansible strut, with the upper inner tubular armwithdrawn into the lower outer tubular arm in the almost fully expandedposition of the strut;

FIG. 2 is a fragmentary longitudinal section similar to FIG. 1 butshowing the first stage in the insertion of the hollow spool-shapedinternal seal between the inner and outer arms;

FIG. 3 is a cross-section along the line 33 of FIG. 2, showing thecompression of the upper or forward end of the internal seal while it isbeing inserted during assembly;

FIG. 4 is a cross-section along the line 44 in FIG. 1, showing theexpanded upper end of the internal seal after insertion; and

FIG. 5 is a fragmentary side elevation of the pivoting upper end of thestrut looking in the direction of the arrows 55 in FIG. 1.

Referring to the drawing in detail, FIGs. l and 5 show anupstroke-cushioning expansible strut, generally designated 10, accordingto one form of the invention as consisting generally of a tubular lowerouter strut arm 12 and a tubular upper inner strut arm 14 reciprocableas a piston within the outer arm 12 as a cylinder and containing aweight-assisting or counterbalancing spring unit 16. The two tubulararms 12 and 14 are slidable relatively to one another in telescopingrelationship but are sealed relatively to one another by a specialspool-shaped elastomeric internal intermediate seal 18 which also actsas a resilient stop and likewise provides additional guidance for thegreatly elongated telescoping arms at locations intermediate theiropposite ends. The lower and upper arms 12 and 14 are connected to alower part of the car body and rear hatch by lower and upper pivotalconnection heads 20 and 22 respectively.

The lower outer arm 12 includes a tubular outer wall, generallydesignated 24, consisting of a lower cylindrical portion 26 havingannular end wall 28 surrounding the lower pivotal connection 20 andcrimped annularly at 30 to an annular groove 32 in the lower head 34 ofthe lower pivotal connection 20. The latter is prefera-- bly a steel oran aluminum casting with its upper surface acting as a spring abutmentfor the outer lower strut arm 12 against which the assist spring unit 16exerts its force. Integral with and extending downward from the lowerhead 34 is a lug 36 which in turn is bored at right angles to thelongitudinal axis of the outer arm 12 to receive a pivot bolt 38. Thepivot bolt 38 is similar to that of the upper pivotal connection 22shown in FIG. 5 and described in detail below, and is secured to a lowerpart of the car body (not shown). The lower head 34 is provided on itsupper surface with an upstanding annular rib 40 which spaces the lowerends of the individual outer and inner assist springs 42 and 44respectively of the spring unit 16. A resilient bushing 37 is assembledbetween the lug 36 of the lower strut arm 12 and the pivot bolt 38,allowing a resilient swiveling action, should the upper and lower pivotbolts not lie in the same plane. This bushing 37 is preferably of ahigh-impact plastic, such as a polyamide plastic containing chips ofpolytetrafluoroethylene plastic. The material for the chips is soldcommercially under the trade name Teflon.

The upper end of the lower cylindrical portion 26 of the outer wall 24is joined to a constricted intermediate cylindrical portion 46 (Fig. 1)by a convergent frustoconical portion 48 integral therewith, whereas theupper end of the constricted cylindrical intermediate portion 46 isjoined to an intermediate cylindrical portion 50 by anupwardly-diverging frustoconical portion 52. The intermediatecylindrical portion 50 of the side wall 24 is joined at its upper end toa reduced diameter upper cylindrical portion 54 by a frusto-conicalconvergent portion 56. The upper cylindrical portion 54 in turn isjoined by an upwardly flaring annular portion 58 to a cylindrical upperend portion 60. A flanged hollow cylindrical upper end external sealingand guiding bushing 62 closes the space between the cylindrical upperend portion 60 and the elongated cylindrical portion 64 of the tubularwall or piston rod 66 of the inner arm 14. The tubular wall 66 isprovided with axiallyspaced lower, intermediate and upper sets ofcoaxial circumferentially-spaced air bleed orifices 65, 67 and 69respectively.

The lower end of the tubular wall or piston rod 66 is provided with aradial flange portion 68 which joins the elongated cylindrical wall 64to a short lower cylindrical end wall portion 70 (FIG. 1). Thisconstruction is strengthened by a plurality of circumferentially-spacedribs 71, one of which is shown at the bottom of FIG. 1. Surrounding thelower end of the tubular wall 66 is an elastomeric annular lower seal 72which with the portions 68 and 70 forms a resilient piston head,generally designated 74, on the lower end of the tubular wall 66. Thelatter has a tapered, upwardly-convergent lower end opening aligned witha correspondinglytapered mouth 77 in the end wall 79 of the resilientpiston head 74. The upper end of the tubular wall or piston rod 66 isclosed by the upper head '76 of the upper pivotal connection 22, whichincludes an offset pivot lug 78 integral with the upper head 76 andextending upward therefrom. The upper head 76 is preferably a steel oran aluminum casting, with its lower surface acting as a spring abutmentfor the upper inner strut arm 14 against which the assist andcounterbalancing spring unit 16 exerts its force. The upper head 76 isjoined to the upper end of the tubular wall or piston rod 66 an annularcrimped portion 82 extending into a lower annular groove 84. The tubularwall or piston rod 66 at its upper end terminates in an annular endportion 86 extending into an annular groove 88. The upper head 76,similarly to the lower head 34, is provided with a downwardly-projectingannular rib 75 which spaces the upper ends of the individual outer andinner assist springs 42 and 44 of the spring unit 16. These springs arepreferably provided with a coating 45 of elastomeric material in orderto prevent any ratchet-like noise while being expanded or contracted.

The offset pivot lug 78 is bored transversely for the reception of anupper pivot bolt 92 which is similar to the lower pivot bolt 36, andwhich passes through a side portion 94 of the vehicle body hatch,generally designated 96. A resilient bushing 91 is assembled between thelug 78 of the upper strut arm 14 and the pivot bolt 92, allowing aresilient swiveling action as described for the lower strut arm 12. Thisbushing is preferably of a high-impact plastic, such as a polyamideplastic containing chips of polytetrafluoroethylene plastic, soldcommercially under the trade name Teflon.

The portion 68 of the piston head 74 and the adjacent annular seal 72are drilled parallel to the axis of the inner arm 14 to receive thetubular value casing 98 (FIG. 1) of a relief valve, generally designated100, the head 102 of which covers the upper end of the tubular casing 98while the stem 104 is urged downward by a helical compression spring 106acting against the enlargement 108 on the lower end of the valve stem104. This elastomeric annular lower seal 72 is preferably of ahigh-impact plastic, such as polyamide plastic containing chips ofpolytetrafluoroethylene plastic, sold commercially under the trade nameTeflon.

The constricted intermediate cylindrical portion 46, the frustoconicalportions 48 and 52 adjacent thereto, and the upper part of the lowercylindrical portion 26 (FIG. 1), together with the tubular wall ofpiston rod 64,-enclose a spool-shaped space 110 which, upon assembly ofthe component parts of the strut 10, is occupied by the spool-shapedhollow elastomeric internal intermediate seal 18. The seal 18, as shownin FIGS. 1 to 4 inclusive, consists of a central hollow cylindrical neckportion 112 with a solid annular lower enlargement 114 on its lower endand a radially slotted annular upper enlargement 116 on its upper end.As the internal seal 18 is made of elastomeric material, such as naturalor synthetic rubber or of a polyamide plastic containing chips ofpolytetrafluoroethylene plastic, sold commercially under the trade nameTeflon, the enlargements 114 and 116 are resilient and the slots 118 inthe upper head 116 provide compressibility thereof to facilitate theinsertion of the internal seal 18 into the spool-shaped chamber 110, inthe manner described below.

Prior to the closing of the lower end thereof by the crimping 30 and bythe insertion of the lower pivotal connection 20, the internal seal 18is inserted within the hollow outer arm 12 by following the procedureshown in FIG. 2. In so doing, the workman assembling the strut 10 pushesthe slotted head 116 of the internal seal 18 into the lower cylindricalportion 26 FIG. 2), whereupon, in passing from the cylindrical portion26 through the convergent portion 48, its lobes 120 be tween its slots118 yield radially inward, as shown in the upper portion of FIG. 2 andin FIG. 3. The assembler continues to push the internal seal 18 inwarduntil the slotted upper enlargement 116 thereof passes upward out beyondthe constricted cylindrical portion 46 into the upwardly-divergingportion 52, whereupon the lobes 120 between the radial slots 118 in theupper enlargement 116 expand outward by reason of the resilientelastomeric material thereof. This causes the radial slots 1 18 betweenthe lobes 120 to widen (FIG. 4). The internal seal 18 comes to rest withthe lower enlargement 114 abutting againstthe convergent wall portion 48and with the upper enlargement 116 occupying the space within theupwardly-flared portion 52. After inserting the upper portion of theupper arm 14, which, I

is being guided by a bullet-nose portion (not shown) and which duringassembly will be discarded, and replaced with the upper head 76, theflared upper'enlargement 116 is prevented from collapsing, therebyholding the internal seal 18 securely in place between i the flaredportions 48 and 52 of the lower arm 12.

In the operation of the upstroke-cushioning expansible strut 10, let itbe assumed that the pivotal connections 20 and 22 have been joined tothe lower part of the car body (not shown) and to the hatch 96 by theirrespective pivot bolts 38 and 92, and that the hatch is in its closedposition extending downward. from its hinges which connect it to the carbody roof. To raise the hatch and open the hatchway at the rearward endof the car body, the user grasps the handle (notshown)on the lower endof the hatch and swings it upward and rearward. During this initialstage of the operation,

the weight of the hatch is counterbalanced by the springs 42 and 44. Asthe hatch is raised, however, and

the struts 10, of which there are two located one each: I

on opposite sides of the hatch, assume a more nearly perpendicularposition relatively to the hatch, the hitherto compressed springs 42 and44 are able to apply their maximum force as they expand. The upwardly accelerating speed of the hatch during the upper part of its openingprocedure, increased by the lifting force im-.

parted to it by the operator, however, is now retarded by the airimprisoned in the cushioning chamber 128 constituting the space betweenthe lower head 114 of the internal seal 18 and the piston head 74. Thelower air bleeds through the lowermost orifices 65 until these pass intothe central bore 122 in the internal seal 18 and are thereby temporarilyclosed by said seal 18.

Thus, the violent metal-to-metal clashingwhich previously occurred inprior expansible struts, when appliedto heavy hatches, is effectivelyprevented by the present invention. The air within the central chamber124 of the inner arm 14 can pass into and out of the upper space 126bounded by the intermediate cylindrical portion 50 and frusto-conicalportion 56 of the outer side wall 24 through the upper air bleedorifices 67 and 69, which are arranged as required by the force exertedand according to the rate of the springs To close the hatch, theoperator reverses the abovedescribed procedure. Grasping the handle onthe nowraised hatch, he pulls downward upon it, thereby causing thetubular upper inner arm 14 to telescope with the tubular lower outer arm12 as the former passes downward into the latter. The air entrapped inthe lower chamber 130 adjacent the base 34 of the lower pivotalconnection escapes into the intermediate cushioning chamber 128 andthence through the air bleed orifices 65 into the inner chamber 124 ofthe inner arm 14 by the opening of the relief valve 100. At the sametime, the helical compression springs 42 and 44 are compressed, therebystoring up energy for assisting in the next opening of the hatch.

We claim:

1. An upstroke-cushioning expansible strut adapted bo be pivotallyconnected between an upwardlyswingable closure structure and an enclosedstructure to which the closure structure is hingedly attached, saidexpansible strut comprising an elongated tubular outer arm having aclosed end and an open end and an outer spring abutment disposed remotefrom said open end and having a pivotal connector disposed adjacent saidclosed end and adapted to be pivotally connected to one of saidstructures,

an elongated tubular inner arm disposed in telescoping relationship tosaid outer arm for relative reciprocation therebetween and having aclosed end and an inner spring abutment disposed remote from the closedend of said outer arm and also having a pivotal connector disposedadjacent said closed end of said inner arm and adapted to be pivotallyconnected to the other of said structures,

elongated counterbalancing spring means disposed between and insubstantially continuous engagement with said outer and inner springabutments and normally urging said arms away from one another andadapted to counterbalance the weight of the closure structure,

an outer sealing element disposed between the open end of said outer armand said inner arm in sealing engagement with said inner arm duringrelative sliding motion therebetween, said outer arm having alongitudinal bore and a pneumatic cushioning chamber with a normallyopenair outlet therefrom and said inner arm having piston means thereondisposed in relative sliding engagement with said bore and movabletoward and away from said cushioning chamber, means responsive to apredetermined relative travel of said arms away from one another forclosing said outlet and for consequently causing said piston means tocompress the thus-entrapped air in said cushioning chamber tocushioningly halt the remaining relative travel of said arms away fromone another subsequent to said closing of said outlet, andunidirectional-flow valve means responsive to relative motion of saidarms away from one another to prevent air flow between opposite sides ofsaid piston means and responsive to relative motion of said arms towardone another to permit such air flow between opposite sides of saidpiston means.

2. An upstroke-cushioning expansible strut, according to claim 1,wherein said valve means is mounted in said piston means for traveltherewith.

3. An upstroke-cushioning expansible strut, according to claim 1,wherein said piston means includes a piston head mounted on said innerarm and having an air passageway therethrough and wherein said valvemeans is mounted in said piston head in unidirectional flow control ofair through said passageway.

4. An upstroke-cushioning expansible strut, according to claim 1,wherein said inner arm has a tapered mouth adjacent and extendingthrough said piston means, and wherein said spring means is disposedwithin said inner arm.

5. An upstroke-cushioning expansible strut, according to claim 1,wherein a tubular inner sealing element of resilient material isdisposed within said outer arm remote from said outer sealing elementand in sealing guiding engagement with said inner arm during relativesliding motion between said arms, said inner sealing element incooperation with said piston means defining said cushioning chamber.

6. An upstroke-cushioning expansible strut, according to claim 5,wherein said air outlet is disposed in said tubular inner arm in spacedrelationship with said piston means, and wherein said inner sealingelement effects closing of said outlet in response to a predeterminedtravel of said piston means toward said inner sealing element.

7. An upstroke-cushioning expansible strut, according to claim 5,wherein said tubular outer arm bore adjacent said inner sealing elementincludes an elongated constricted portion, and wherein said innersealing element has a reduced-diameter intermediate portion matinglyengaging said constricted portion and has axially-spaced enlarged headsat opposite ends of said reduced-diameter portion disposed in matingengagement with said bore at opposite ends of said constricted portion,and also has a central bore therethrough relatively slidably receivingand sealingly engaging said tubular inner arm.

8. An upstroke-cushioning expansible strut, according to claim 7,wherein one of said heads has circumferentially-spaced longitudinallyand transverselyextending slots therein defining longitudinally andtransversely extending portions between said slots.

9. An upstroke-cushioning expansible strut, according to claim 1,wherein said tubular outer arm bore has an approximately spool-shapedconstricted internal chamber therein and wherein said sealing element isalso approximately spool-shaped and disposed in sealing matingengagement with said spool-shaped chamber and has a central boretherethrough relatively slidably receiving and engaging said innertubular arm.

1. An upstroke-cushioning expansible strut adapted bo be pivotallyconnected between an upwardly-swingable closure structure and anenclosed structure to which the closure structure is hingedly attached,said expansible strut comprising an elongated tubular outer arm having aclosed end and an open end and an outer spring abutment disposed remotefrom said open end and having a pivotal connector disposed adjacent saidclosed end and adapted to be pivotally connected to one of saidstructures, an elongated tubular inner arm disposed in telescopingrelationship to said outer arm for relative reciprocation therebetweenand having a closed end and an inner spring abutment disposed remotefrom the closed end of said outer arm and also having a pivotalconnector disposed adjacent said closed end of said inner arm andadapted to be pivotally connected to the other of said structures,elongated counterbalancing spring means disposed between and insubstantially continuous engagement with said outer and inner springabutments and normally urging said arms away from one another andadapted to counterbalance the weight of the closure structure, an outersealing element disposed between the open end of said outer arm and saidinner arm in sealing engagement with said inner arm during relativesliding motion therebetween, said outer arm having a longitudinal boreand a pneumatic cushioning chamber with a normally-open air outlettherefrom and said inner arm having piston means thereon disposed inrelative sliding engagement with said bore and movable toward and awayfrom said cushioning chamber, means responsive to a predeterminedrelative travel of said arms away from one another for closing saidoutlet and for consequently causing said piston means to compress thethusentrapped air in said cushioning chamber to cushioningly halt theremaining relative travel of said arms away from one another subsequentto said closing of said outlet, and unidirectional-flow valve meansresponsive to relative motion of said arms away from one another toprevent air flow between opposite sides of said piston means andresponsive to relative motion of said arms toward one another to permitsuch air flow between opposite sides of said piston means. 2.Anupstroke-cushioning expansible strut, according to claim 1, whereinsaid valve means is mounted in said piston means for travel therewith.3. An upstroke-cushioning expansible strut, according to claim 1,wherein said piston means includes a piston head mounted on said innerarm and having an air passageway therethrough and wherein said valvemeans is mounted in said piston head in unidirectional flow control ofair through said passageway.
 4. An upstroke-cushioning expansible strut,according to claim 1, wherein said inner arm has a tapered mouthadjacent and extending through said piston means, and wherein saidspring means is disposed within said inner arm.
 5. Anupstroke-cushioning expansible strut, according to claim 1, wherein atubular inner sealing element of resilient material is disposed withinsaid outer arm remote from said outer sealing element and in sealingguiding engagement with said inner arm during relative sliding motionbetween said arms, said inner sealing element in cooperation with saidpiston means defining said cushioning chamber.
 6. An upstroke-cushioningexpansible strut, according to claim 5, wherein said air outlet isdisposed in said tubular inner arm in spaced relationship with saidpiston means, and wherein said inner sealing element effects closing ofsaid outlet in response to a predetermined travel of said piston meanstoward said inner sealing element.
 7. An upstroke-cushioning expansiblestrut, according to claim 5, wherein said tubular outer arm boreadjacent said inner sealing element includes an elongated constrictedportion, and wherein said inner sealing element has a reduced-diameterintermediate portion matingly engaging said constricted portion and hasaxially-spaced enlarged heads at opposite ends of said reduced-diameterportion disposed in mating engagement with said bore at opposite ends ofsaid constricted portion, and also has a central bore therethroughrelatively slidably receiving and sealinglyengaging said tubular innerarm.
 8. An upstroke-cushioning expansible strut, according to claim 7,wherein one of said heads has circumferentially-spaced longitudinallyand transversely-extending slots therein defining longitudinally andtransversely extending portions between said slots.
 9. Anupstroke-cushioning expansible strut, according to claim 1, wherein saidtubular outer arm bore has an approximately spool-shaped constrictedinternal chamber therein and wherein said sealing element is alsoapproximately spool-shaped and disposed in sealing mating engagementwith said spool-shaped chamber and has a central bore therethroughrelatively slidably receiving and engaging said inner tubular arm.